[redandwhitE]

Bought my first 45 diesel last year and although not fast, I was happy with it. Bought the second one and realised this had much more power/acceleration than the first one. Realised first one had a fault and been meaning to get the it looked at but not got there yet.

Now the second has lost power and by considerably more than the first one. It's precarious when pulling out and only when up towards 3000 rpm and beyond, does it move on but even then, nowhere near as it did when purchased.

My mechanical knowledge is limited but I'd imagine it's the turbo(s) and perhaps the waste gate not fully functioning. If so, is this something the keen amateur (me) could diagnose and subsequently repair?

As both are below par, it's now time to sort them out so any start points would be appreciated.

[220 GSi turbo]

It is most probably the MAF (mass air flow) sensor which is in the black tube with wires connected to it between the air filter and engine. These degrade with time and the ECU relies on the signal from the MAF to determine how much fuel to send to the injectors.

If cleaning the MAF sensor does not help, the fix is to fit a new one (ideally genuine Bosch, not a much cheaper alternative) or to fit a compensator device which I believe amplifies the signal from the MAF sensor.
I have one of them fitted to my 25 diesel and it was bought several years ago from https://www.tuning-diesels.com/ (also known in the past as 'Rover Ron') although I have looked tonight and they no longer list the Rover 25/45, ZR, ZS etc. The products they sell for the older 220/420/620 SDi cars and for the 75/ZT range are probably not compatible, so it would be a good idea to contact them and ask first.

However, you should also check that the intercooler and its hoses are not leaking, as any boost pressure lost will obviously affect performance. Boost leaks are usually accompanied by black smoke from the exhaust, as the engine is not getting enough air to deal with the fuel that the ECU has sent to it. This would generally affect performance under acceleration, rather than the first few moments from standstill.

[Montegoman]

We have had a similar issue on two of our 25 diesels and on both occasions it was the MAF sensor.

[Russnp]

CJL tuning in spalding is worth contacting as he does remaps on the L series and keeps quite a few spares .
My ZR had had a few mods done to it before I bought it CJL remapped it which gave it more power, better economy and no smoke

[redandwhitE]

Thanks for the pointers.

I've got a MAF sensor on the way and will try it on both cars. If it solves the problem, I'll order a second one.

For info, there's no smoke to speak of although one does burn a little oil. Will keep you informed.

[redandwhitE]

As promised, here's an update:

Whilst waiting for the MAF Sensor, I disconnected the existing one and the car drove practically as good as it ever did. I'm guessing without the sensor, it resorts to a default setting that is good without being optimum. I've now changed the sensor, re-plugged it in and all is well.

A strange event happened when we had heavy rain and plenty of standing water however. When I drove through a large puddle, the car responded and picked up momentarily to close to its optimum performance. For a second or two, the engine provided full revs. This was with the existing MAF sensor still connected. I can only imagine the water was bridging a split/hole in a pipe or something. Anyway, I've replaced a couple of lengths of vacuum pipe that were split so that can only help.

Thanks to those who suggested the MAF sensor.....speeded up diagnosis.

Cheers Richard

[RoverTD]

Richard
I have the same problem, since it was contaminated by water spray earlier in the year. Did you get a new Bosch MAF or some other make? Thanks Derek

[redandwhitE]

I just ordered one from my local motor factors but can't recall the brand. Definitely not Bosch as it was only just over £40. Not with car for a few days but will see if there's 'owt written on it when I get back.

[RoverTD]

I have just unplugged the MAF and its running much better , more bottom end power and smoother pick up all round, so a new MAF required or not bother connecting it up again!

[220 GSi turbo]

If you leave it unplugged, the engine speed tops out at around 3000-3500 rpm.